I only learned it when taking some linguistics classes in college. I have rarely used it outside of those few assignments.
In the US, there isn't much standardization with phonetic transcriptions. I do teach my students how to use a dictionary, and one of the things I have to remind them is that the phonetic representation may vary from dictionary to dictionary, and that they need to consult the pronunciation key provided in the dictionary they're using.
I frequently use this
site, when dealing with particular pronunciation problems, because it has excellent animated side-views of the articulatory tract as well as frontal view of the mouth. The downside is that it's based on IPA, so I have to tell the students to ignore the symbols. I just project the website so they can see the animations and videos, and as much as possible avoid showing the IPA symbols.
IPA can be very confusing since many of the symbols are just regular alphabet letters, but those letters don't always match up the alphabetic representation we use for that sound.
For example, my Spanish speaking students frequently pronounce the letter 'y' (IPA /j/) as a 'j' (IPA /ʤ/). It's very confusing then to try to use IPA symbols where 'y' is represented by /j/.
I think IPA has its uses, but not in an ESL classroom.